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Effect of post-thermal annealing on the structural and optical properties of ZnO thin films prepared from a polymer precursor

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Chinese physics B 2012年第7期21卷 551-558页

作者： Jijoy.p.Mathew George Varghese Jacob Mathew Thin Film Research Laboratory Department of PhysicsSt.Berchmans CollegeChanganasseryKerala 686101India department of physics Calicut UniversityThenjippalamKeralaIndia

ZnO thin films were synthesised by a new method which uses polyvinyl alcohol （pVA） as the polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and time. All the films possess tensile strain, which relaxes as the annealing temperature and time increase. The photoluminescence （pL） spectra contain only ultraviolet （UV） peaks at low temperature, but as the annealing temperature and time increase, we observe peaks at the blue and green regions with a variation in the intensities of these peaks with annealing temperature and time.

关键词： stress, band gap, Urbach energy photoluminescence

BL Lacertae: Hard Optical Spectrum and GeV γ-ray Emission

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Chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 231-246页

作者： Shan-JieQian Xi-ZhenZhang T.p.Krichbaum NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 Max-planck-InstitutfürRadioastronomie AufdemHügel6953121BonnGermany

The spectral energy distribution (SED) of the γ-ray flare observed inJuly 1997 in BL Lacertae is re-considered. It is pointed out that the optical observa-tions made by Webb et al. showed the associated optical flare has a hard spectrum(the average spectral index αopt～ 0.48, F_v∝v^(-α)), and the ASCA observationsmade by Tanihata et al. showed very steep spectra in the soft X-ray band (0.7-1.5 keV) (α_x～3-4). We find that the flux densities and spectral indices in both theoptical and soft X-ray bands are closely consistent with a ‘canonical' synchrotronspectrum emitted by relativistic electrons of a power-law energy distribution witha high energy cutoff, and thus the peak of the SED of the synchrotron radiation (inrepresentation of vF_v) is located in the EUV -- soft X-ray bands. Therefore, theGeV γ-ray emission observed in the July 1997 outburst may be mainly due to thesynchrotron self-Compton (SSC) process, contrasting with the current explanationsin terms of external radiation Compton (ERC) process, in which the seed photonsare mostly taken to be the UV emission from the clouds of the broad emission lineregion. We argue that the hard optical spectra observed during the γ-ray outburstmay be an important signature for the acceleration of high energy electrons (γ_e～10~4)in the γ-ray emitting region.

关键词： galaxies:compact gamma rays:observations quasars:individual:BL Lacertae

Drag-free and Attitude Control for Long-distance,Low-Earth-orbit,Gravimetric Satellite Formation

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Drag-free and Attitude Control for Long-distance,Low-Earth-o...

XRpD and SEM-EDS Identification of a Mineralogical Standards Kit Forming a 19th Century Collection for Educational Analysis

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作者： Enrico CANUTO luca MASSOTTI Andres MOLANO-JIMENEZ Carlos Norberto pEREZ politecnico di Torino Dipartimento di Automatica e Informatica

Following the launch in Spring 2009 and operations of the GOCE satellite（Gravity field and steady state Ocean Circulation Explorer）,a new mission made bya long-distance（10 km）satellite formation is under study by European Space *** aims at monitoring,during a 6-year mission,Earth’s gravity field fluctuations more or less in the same wavelength band of GOCE（around 100-km Earth surface grid）.As GOCE is the first’truly’drag-free satellite,the envisaged formation is expected to be the first drag-free formation,posing a suite of challenging technology and control problems under study and solution,*** have demonstrated the mission must be *** paper concentrates on a triad of control problems to be solved and coordinated,namely formation,drag-free and attitude,all of them being highly constrained by a long-life low-Earth-orbit mission imposing low propellant mass and therefore electric propulsion,by scarce propulsion throttabilityof electric thrusters and limited electric *** will be presented and how they can be met through Embedded Model Control will be *** simulated results are included.

关键词： Satellite Formation Drag-free Attitude Control Low-Earth-orbit Gravimetry

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Journal of Minerals and Materials Characterization and Engineering 2016年第1期4卷 73-86页

作者： Emanuele Costa Alessandro delmastro luca Di Gregorio Silvia Ronchetti Massimo Umberto Tomalino department of Earth Science University of Turin Torino Italy department of Applied Science and Technology (DISAT) Polytechnic University of Turin Torino Italy Former department of Applied Science and Technology (DISAT) Polytechnic University of Turin Torino Italy

An historical collection of more than one hundred samples of minerals and ore, used in the second half of the XVIII century was found and acquired during Munich Mineralientage 2014. The samples contained in numbered glass vials but lacking description, were prepared for teaching purpose about determinative mineralogy and ore recognition. All samples were analysed and identified. The identification effort drove the authors along a historical excursus about the didactics of mineralogy and the dry method analysis, nowadays neglected.

关键词： Blowpipe XRpD SEM-EDS Historical Collection Dry Analysis Ore Identification

Isothermal study of effusion cooling flows using a large eddy simulation approach

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航空动力学报 2009年第4期24卷 729-739页

作者： W.p.Bennett J.J.Mc Guirk Aeronautical and Automotive Engineering department Loughborough University

An isothermal numerical study of effusion cooling flow is conducted using a large eddy simulation(LES) *** main types of cooling are considered,namely tangential film cooling and oblique patch effusion *** represent tangential film cooling,a simplified model of a plane turbulent wall jet along a flat plate in quiescent surrounding fluid is *** contrast to a classic turbulent boundary layer flow,the plane turbulent wall jet possesses an outer free shear flow region,an inner near wall region and an interaction region,characterised by substantial levels of turbulent shear stress *** shear stress characteristics hold significant implications for RANS modelling,implications that also apply to more complex tangential film cooling flows with non-zero free stream *** LES technique used in the current study provides a satisfactory overall prediction of the plane turbulent wall jet flow,including the initial transition region,and the characteristic separation of the zero turbulent shear stress and zero shear strain *** effusion patch cooling is modelled using a staggered array of 12 rows of effusion holes,drilled at 30° to the flat plate *** effusion holes connect two channels separated by the flat ***,these comprise of a channel representing the combustion chamber flow and a cooling air supply channel.A difference in pressure between the two channels forces air from the cooling supply side,through the effusion holes,and into the combustion chamber *** from successive effusion rows coalesces to form an aerodynamic film between the combustion chamber main flow and the flat *** practical applications,this film is used to separate the hot combustion gases from the combustion chamber *** numerical model is shown to be capable of accurately predicting the injection,penetration,downstream decay,and coalescence of the effusion *** addition,the numerical model captures entrainmen

关键词： effusion cooling large eddy simulation isothermal analysis film cooling turbulent wall jet

pOLYMERIC SURFACTANT STRUCTURE

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Chinese Journal of polymer Science 2001年第2期19卷 135-145页

作者： p.M.Saville J.W.White Research School of Chemistry The Australian National University Canberra ACT 0200 AustraliaResearch School of Chemistry The Australian National University Canberra ACT 0200 Australia

polymeric surfactants are amongst the most widespread of all polymers. In nature, proteins and polysaccharidescause self organization as a result of this surfactancy; in industry, polymeric surfactants play key roles in the food, explosivesand surface coatings sectors. The generation of useful nano- and micro-structures in films and emulsions as a result ofpolymer amphiphilicity and the application of mechanical stress is discussed. The use of X-ray and neutron small anglescattering and reflectivity to measure these structures and their dynamic properties will be described. New results on linear and dendritic polymer surfactants are presented.

关键词： polymeric Surfactant Structure X-ray Neutron Reflectivity Film

Mechanical behavior of iron ore tailings under standard compression and extension triaxial stress paths

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1883-1894页

作者： Alexia Cindy Wagner João paulo de Sousa Silva João Vítor de Azambuja Carvalho Ana Luisa Cezar Rissoli pedro pazzoto Cacciari Helder Mansur Chaves Hugo Carlos Scheuermann Filho Nilo Cesar Consoli Universidade Federal do Rio Grande do Sul Porto Alegre90035-190Brazil Mineral development Centre Vale S.A.Santa Luzia33040-900Brazil department of Civil Geological and Mining EngineeringPolytechnique MontrealMontrealH3C 3A7Canada

The disposal of mining tailings has increasingly focused on the use of dry *** structures offer more security since they use filtered and compacted *** of the construction method and the heights achieved,the material that compounds the structure can be subjected to different stress paths along the failure *** theoretical framework considered in the design of these structures generally is the critical state soil mechanics(CSSM).However,the data in the literature concerning the uniqueness of critical state line(CSL)is still controversial as the soil is subjected to different stress *** respect to tailings,this question is even more *** paper studies two tailings with different gradings due to the beneficial processes over extension and compression paths.A series of drained and undrained triaxial tests was conducted over a range of initial densities and stress *** the q-p'plane,different critical stress ratio(M)values were obtained for compression and extension stress ***,the critical state friction angle is very similar with a slightly higher critical state friction angle for extension *** stress path dependent CSLs were obtained in the n-lnp0 plane with the extension tests below the CSL defined in *** the fines content,the studied tailings presented very similar M and critical state friction angle ***,the fines content af-fects the volumetric behavior of the studied tailings and the CSLs on the n-lnp0 plane shift downwards with the increasing fines content for compression and extension *** relation to dilatancy analysis,the fines content did not present an evident influence on the dilatancy of the ***,different values of mean stress ratio N were obtained between compression and extension tests and can corroborate the existence of non-unique CSLs for these materials.

关键词： Iron ore tailings(IOTs) Dry stacking Critical state soil mechanics Extension tests Stress path

Nonlinear ion-acoustic solitary waves in an electron-positron-ion plasma with relativistic positron beam

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Chinese physics B 2018年第10期27卷 471-476页

作者： Ridip Sarma Amar p Misra Nirab C Adhikary department of Mathematics University of Science and TechnologyTechno CityKhanaparaBaridua9th MileRi-BhoiMeghalayaIndia department of Mathematics Siksha BhavanaVisva-Bharati University physical Sciences Division Institute of Advanced Study in Science and TechnologyVigyan PathPaschim BoragaonGarchukGuwahati-781035AssamIndia

The propagation characteristics of nonlinear ion–acoustic（IA） solitary waves（SWs） are studied in thermal electron–positron–ion plasma considering the effect of relativistic positron beam. Starting from a set of fluid equations and using the reductive perturbation technique, we derive a Korteweg–de Vries（KdV） equation which governs the evolution of weakly nonlinear IA SWs in relativistic beam driven plasmas. The properties of the IA soliton are studied, and it is shown that the presence of relativistic positron beam significantly modifies the characteristics of IA solitons.

关键词： electron-positron-ion plasma relativistic effect ion-acoustic wave homogeneous balance method

Computational Study of performance Characteristics for Truncated Conical Aerospike Nozzles

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Journal of Thermal Science 2017年第6期26卷 483-489页

作者： prasanth p Nair Abhilash Suryan Heuy Dong Kim department of Mechanical Engineering College of Engineering Trivandrum department of Mechanical Engineering Andong National University

Aerospike nozzles are advanced rocket nozzles that can maintain its aerodynamic efficiency over a wide range of altitudes. It belongs to class of altitude compensating nozzles. A vehicle with an aerospike nozzle uses less fuel at low altitudes due to its altitude adaptability, where most missions have the greatest need for thrust. Aerospike nozzles are better suited to Single Stage to Orbit （SSTO） missions compared to conventional nozzles. In the cur- rent study, the flow through 20% and 40% aerospike nozzle is analyzed in detail using computational fluid dy- namics technique. Steady state analysis with implicit formulation is carried out. Reynolds averaged Navier-Stokes equations are solved with the Spalart-AUmaras turbulence model. The results are compared with experimental results from previous work. The transition from open wake to closed wake happens in lower Nozzle pressure Ratio for 20% as compared to 40% aerospike nozzle.

关键词： aerospike nozzle plug nozzle advanced rocket nozzles thrust coefficient base pressure.